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Physiology. — #The principle of entropy in physiology.” By Dr. 
J. W. LANGELAAN. 3'¢ part. (Communicated by Prof. T. Pracr). 
All investigations made with the intention of testing the law of Fecunnr 
at the experiment, have proved, that this law is only satisfied within 
a small interval and within that interval only by approximation. 
In order to find out the causes of these deviations, I have tried 
to deduce the law of Frcuner (considered as a physiological law) 
from a general physical principle. It has appeared from this deduction 
that this formula rests on very special premises, and that the cireum- 
stances assumed in these premises, are never realized in nature. 
In a series of experiments I have tried to fulfil as accurately as 
possible the conditions required by this law according to its dedue- 
tion. To this purpose the spinal cord of a frog *) was cut between 
the cranium and first vertebra; then the whole frog, with exception 
of the hind leg which was used for the experiment, was wrapped 
up in wads and fastened to a glass rod. The leg hung down in a 
wide vessel which could contain about 600 ccm. of fluid. In the sole 
of the foot a hook was put and a horsehair was attached to this hook, 
which passed outside through a very small opening in the bottom of 
the vessel. This horsehair was fixed to the arm of a length-recorder. 
The small opening through which the hair passed was filled up 
with vaseline; this prevented almost perfectly the fluid to drip out, 
while the friction experienced by the horsehair was very slight. By 
suspending a weight to the length-recorder the leg was charged with 
15 grams. Then the vessel was filled with 350 eem. of water, and 
the lee immersed till the knee. To the stand bearing the glass and 
the frog, a clamp was fixed bearing a burette. This burette contained 
a solution of oxalic acid in distilled water. By opening the tap this 
solution flowed into the water in which the leg hung. A bent stirrer 
always kept in slow motion (but which did not touch the leg), caused 
the acid to be thoroughly mixed with the fluid. Then so much acid 
was slowly added to the liquid till the leg began to contract. The 
vertical motion of the leg, three times magnified, was registered on a 
slowly rotating cylindre by the length-recorder. In order to prevent 
too large excursions, the length-recorder struck against a piece of cork, 
so that the contraction in the beginning took place isotonically, at 
the end isometrically. 
After the leg had returned to rest, we waited about 5 minutes and 
1) Small male specimens of Rana esculenta proved to be the most suitable for 
the experiment, 
